In the field of wireless networking, modern mobile stations, such as cell phones or wireless broadband-equipped laptops, typically utilize a radio access network (RAN) to connect to a packet data network (PDN), by which they gain access to hosts on the Internet via Internet Protocol (IP). This connectivity is provided by mobile network operators, which build and maintain networks of radio access points, networking switches and gateways, and high-bandwidth links.
As a mobile station moves, such as from one radio tower to another radio tower, it can pass into areas of the network controlled by different equipment, such as a packet data serving node (PDSN), in some cases requiring a handoff. However, mobile network operators may have different technologies implemented on their networks, and not all equipment may be upgraded to the same technology at the same time. As a result, some handoffs take place that involve the mobile station being handed off to a radio network using a different radio network technology.
Two such radio network technologies are known as Long-Term Evolution (LTE) and Evolved High Rate Packet Data (eHRPD). The LTE standards are published by the 3rd Generation Partnership Project (“3GPP”), a not-for-profit industry consortium. The eHRPD standards are published by a similar consortium called the 3rd Generation Partnership Project 2 (“3GPP2”).